In present day data processing systems most of the circuits and more specifically the logic circuits are in the form of integrated circuits. Efforts continue to be made to increase the density of integration of the circuit components on a single semiconductor substrate or chip. In a typical system there may be a hundred such chips in one thermal controlled module (TCM). There may be several TCM's a computer system. For today's bipolar logic chips logic performance (speed) is largely a function of the power that is available for the critical logic paths. For chips with five thousand or more logic gates, the power budget indeed limits the speed of the computer system it is used in. Push-pull drivers are widely used on these logic logic chips in all off chip applications. There is a need for efficient current drivers for driving signals between chips. FIG. 1 labeled prior art is a typical push pull driver circuit for driving between chips which use differential cascode current switch circuitry as disclosed generally in a IBM Corporation U.S. Pat. No. 4,513,283 of Lininger entitled "Latch Circuits with Differential with Cascodes Current Switch Logic", U.S. Pat. No. 4,760,289 of Eichelberger et al. entitled "Two Level Differential Cascode Current Switch Masterslice" and Low U.S. Pat. No. 4,686,392. These patents are incorporated herein by reference. This driver is particularly for use with differential cascode circuitry which requires lesser current and is lower power than ECL circuitry. The logic is provided by a pair of wires and for a logic "1" level 0.6 volts is on one lead and 0.4 volts on the other lead for and for logic "0" the levels are reversed. A 20 percent increase in performance is achieved using this differential cascode current switch as compared with ECL masterslice circuits running the same power. The prior art circuit shown in FIG. 1 is a push pull driver using as a predriver the differential cascode current switch circuitry. As discussed previously the driver of FIG. 1 is used between chips within a given TCM or between TCM's for example, and maybe used further for cabling or outbound connections. Differential cascode circuit has two wires for input and that being at the -A and +A terminals in FIG. 1. A single ended output is at terminal B. The circuit of FIG. 1 includes large power transistors 10 and 11 connected in series between VCC and VT with the junction J of the transistors being coupled to the output terminal B. A differential cascode current switch predriver including transistors 12 and 13 is coupled between VCC and VEE. The differential signal at +A and -A steers the current through transistors 12 and 13. The voltage drop across the collector resistor of transistor 12 controls the conduction or cutoff of transistor 10. The conduction and cutoff of lower transistor 11 is provided by the emitter follower circuit including transistor 16 and resistors 14 and 15. This emitter follower circuit provides level shifting to prevent saturation of the input stage transistor 13. Without the emitter follower COC would have to be very low voltage causing T13 to saturate. The node at COC can get too low such that the base is higher than the collector. The emitter follower prevents this and further provides current gain to get better drive.
This emitter follower circuit, however, dissipates about 3.6 milliwatts of power per driver. This results in a typical TCM with many drivers to an average of 17 watts. This makes for additional cooling and in particular can necessitate a water cooling system and the attendant additional costs.